1. Field of the Invention
This invention relates to a safety device for a lift, and more particularly to a safety device for protecting fall of a lift for vehicles during painting, coating, and/or sheet metal working for automobiles, or the other working operations being performed.
2. Prior Art
A lift for vehicles which is well known in the art is shown in FIG. 1 and 2. The previous lift comprises an elevating mechanism (b) being installed on a lower frame (a) and cradles (c) provided on the upper end of the elevating mechanism, in which the elevating mechanism includes a link mechanism (d) constructed in parallelogram and a hydraulic cylinder (e), one end of the hydraulic cylinder opposite to its rod (f) being pivoted at the lower frame and one end of the rod (f) opposite to the cylinder portion also pivoted at an upper frame (g) or the upper side of the link mechanism (d) in parallelogram, the cradles (c) being elevated up and down by forward and backward movements of the rod (f) which is driven by the hydraulic cylinder.
In FIGS. 1 and 2, a safety device for protecting fall of a lift of the previous type comprises a rack (h) provided on the lower frame (a), and a stopper shaft (i) in which one end is pivoted to the upper frame (g) and another free end can be in engagement with the rack (h). The device is constructed such that one end of a lever (k) having a cam (j) is inserted into a bore formed at the free end of the stopper shaft (i), with movement of the lift being raised up, the free end of the stopper shaft (i) moves over teeth of the rack (h) one by one to the left in FIG. 2. In case oil pressure applied to the hydraulic cylinder (e) is released when the lift is raised up to a desired position, then, as it is shown in FIG. 3 by solid lines, the free end of the stopper shaft (i) comes into engagement with an adjacent tooth of the rack (h) to prevent the lift from falling down. When the lift is let down, the cam (j) is forced to stand in a upright position, as shown in FIG. 3 by dotted lines, by an operator's manual rotation of the lever (k), so that the free end of the stopper shaft (i) is disengaged to move over the teeth of the rack (h) to the right in FIG. 3.
However, the safety device for protecting fall of a lift described in the above has such drawbacks that a gap between the bore at the free end of the stopper shaft (i) and the end of the lever (k) inserted within the bore is apt to be filled with dust or it rusts therebetween so that the lever (k) may be obstructed of its smooth rotation, which may possibly invite dangerous situations such that the cam (j) is left standing, as shown in FIG. 3 by dotted lines, without being turned down to be engaged with a teeth of the rack (h). Also, because of the construction described as above, the device should be manufactured so accurate that it becomes more expensive.